Is the Mitsubishi engine in a 642B freewheeling or is it an interference engine that will bend valves if the timing belt breaks? My service manual doesn't list an interval for changing the timing belt (if you can even get them now) so I'm hoping that the low horsepower of the engine compared to the car version means that there's enough clearance for the pistons to miss the valves in case the belt breaks. It obviously is a different version than the car engines, with the blocked-off second barrel in the carburetor,etc., so I'm wondering if the "industrial" version has a lower compression ratio, or recesses in the piston heads or something. Does anyone know, or have you broken a belt and had the engine survive?